The present invention generally relates to furnaces and, more particularly, relates to high temperature furnaces having improved energy efficiency and pollutant prevention capabilities.
According to a recent DOE Interlaboratory Working Group Report, in 1997, the U.S. industrial sector consumed approximately 35 quads of primary energy resulting in about 494 MtC of carbon emissions. More than half of this energy was used as production process heat by energy-intensive industries like steel, metal casting, aluminum, chemicals, paper, and glass. However, only approximately 60% of this energy is used/usable and, thus, approximately 40% is lost through inefficiencies. This significant amount of lost energy costs approximately $21 billion. Moreover, a byproduct of this energy usage is the corresponding CO2 emissions that contribute to global warming.
In order to reduce fuel expenses and CO2 emissions, it is important to increase the furnace efficiencies. Such efficiency improvements can be achieved by better insulation (reducing conductive, convective, and radiative losses) and by reducing stack losses. The present invention is capable of reducing stack losses, which is a major contributor to these losses.
Accordingly, the wasted flue gas enthalpy will be used to preheat the incoming oxygen-enriched combustion air and fuel. Typically, this method is not employed because both preheating and oxygen-enrichment increase NOX production and contributes to heat flux non-uniformities within the furnace because of higher flame temperatures. A novel solution to this problem is addressed by the present invention. That is, the present invention utilizes nearly homogeneous burning and increases the flame radiation. Therefore, near unity flame emissivity at an average temperature of 1700K, with peak temperatures not exceeding 1800K, is accomplished. Thus, the present invention provides nearly uniform radiation heat transfer to the objects in the furnace at a magnitude exceeding 400 kW/m2, while maintaining strict constraints on NOX, CO, unburned hydrocarbons (UHC) and particulate emissions. The level of heat flux attained is nearly twice the current maximum, thereby enabling an increase in the furnace productivity or a decrease in size and cost.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. For example, this invention could be used to increase the efficiency of water-tube boilers or a multiple zone furnace can be designed based on the concepts outline herein.